A cellular communication network is a wireless communication network where one or more wireless devices communicate with one or more radio base stations, RBSs, possibly organized in one or more cells.
Examples of such cellular communication networks include wireless networks implementing global system for mobile communications, GSM, wideband code division multiple access, WCDMA, or long term evolution, LTE, radio access technologies, RATs, or any other RAT defined by, e.g., the 3rd generation partnership project, 3GPP.
Other examples of cellular communication networks include networks implementing the RATs of the third, fourth and fifth generation communication systems, 3G, 4G, 5G, and also wireless local area networks, WLANs.
The wireless signals transmitted by the one or more RBSs may interference with each other. This interference is herein referred to as inter-cell interference. A large amount of inter-cell interference is undesirable since inter-cell interference generally degrades network performance.
RBSs in general consume significant amounts of power during operation, which power consumption drives the cost of operating a network. Thus, in order to lower operating costs in cellular communication networks, it is often desired to reduce RBS energy consumption.
An RBS which serves no traffic can in some circumstances enter into a dormant mode and thereby reduce both network energy consumption and inter-cell interference. This technique of entering dormant mode is especially interesting for small capacity RBSs which are covered by an umbrella or macro RBS in a heterogeneous network scenario.
When an RBS or cell goes into dormant mode it becomes invisible for the wireless devices in the communication network. Hence it is a quite drastic action to take. Instead of entering dormant mode, an active RBS can take several, less drastic, actions in order to reduce energy consumption and/or inter-cell interference.
For instance, as an alternative to entering dormant mode, an RBS serving a multi-sector cell can reduce the number of active antennas, going from a multi-sector configuration into a single sector configuration which only uses a single omni-directional antenna.
An RBS can also, instead of entering dormant mode, reduce its signaling bandwidth used for communication with wireless devices and other RBSs, e.g., by replacing an active wide-band cell with a narrow-band cell.
Thus, RBSs can switch between two or more performance modes, i.e., operating modes in which the RBS provides different performance levels. However, during switching between such different performance level configurations, the performance of an RBS may be temporarily degraded.
As an example of this temporary performance level degradation, consider a re-configuration from a single sector antenna mode into a multi-sector mode of operation in an RBS. In this case a handover of served wireless devices between the single-sector set-up RBS and the new multi-sector set-up RBS may be necessary. This handover drives signaling overhead and also increases the risk of radio link failure. In case the single-sector cell and the multi-sector cells are active simultaneously during the transition between different levels of performance, the interference level in the network is increased, which can temporarily degrade user throughput in the network.
Thus, the performance of an RBS which is switching from a presently configured reduced performance mode into an increased performance mode can actually first decrease below the reduced performance level before increasing up to the new, higher, performance level. A temporary reduction in RBS performance due to performance level re-configuration will herein be referred to as a re-configuration penalty.
Because of this re-configuration penalty, a wireless device entering a cell having a reduced performance level, and wherein the wireless device requires a higher service level than presently offered in the cell, may initially experience worsened conditions as the RBS performance level is re-configured from the reduced level into a higher performance level.